John Oliver, about to return to HBO, and his secrecy policy

NEW YORK (AP) - HBO's John Oliver says he likes the idea of keeping as much as possible about his show a secret until it airs each week, a philosophy he took to the extreme last spring when he traveled to Moscow to interview Edward Snowden.

Oliver, who begins a new round of his "Last Week Tonight" comedy show on Feb. 14, did not tell his network until he had returned that he had spoken to the fugitive, who leaked NSA documents to journalists in 2013 and faces prison time if he returns to the United States.

He pleaded with HBO not to tell anyone that he had interviewed Snowden, in part because it would spoil a segment where he makes viewers wonder if Snowden would even show up. He even asked the studio audience at the episode's taping to keep quiet about it online.

"I really appreciated the fact that HBO would let us do it that way," Oliver said, "because we thought it was the best way to actually present it, even though commercially it was the worst way you could present it."

Oliver said HBO has kept its promise not to interfere creatively in the making of "Last Week Tonight."

"It's like your parents saying, 'you can do whatever you'd like, but don't touch that cabinet," he said. "I presumed that HBO was lying" the way other networks often do, he said.

With his philosophy in mind, Oliver was not revealing much on Wednesday about the topics "Last Week Tonight" will be covering in the upcoming months. It's difficult to reveal much because some stories may fall through, he said. Each week's show has a centerpiece story that is discussed in a mixture of comedy and reporting.

He will, however, be ending a moratorium about discussion of the presidential campaign. The show wants to look almost forensically at how the process of democracy works, rather than be caught in daily stories about what candidates are saying that he said can be handled better comically elsewhere.

"Otherwise, you get lost in the general campaign ephemera where nothing really significant happens of any consequence," he said.

He hopes for more long-gestating stories like his examination or religious fundraising, after which he and actress Rachel Dratch posed as televangelists asking viewers to send them one dollar.

Joke or not, "Last Week Tonight" received some $70,000 in single dollar bills - along with five vials of semen, at least three of which Oliver is convinced were fake. The money was donated to Doctors Without Borders.

Oliver and his staff work at what must be one of the most interesting office buildings in New York, one floor below CBS' "60 Minutes" staff and a few floors away from where Samantha Bee, fellow alumnus of "The Daily Show," is making her upcoming TBS show.

"An elevator ride with Charlie Rose is time well spent," Oliver said.